handle resource leaks

[dustin-decker]

Description

This MR cleans up resource leaks of response bodies.

There are a few categories of changes:

• closing resp.Body when the response is not returned and the interface{} provided to client.Do() is nil
• instructing the caller to close resp.Body when a response is returned and the interface{} provided to client.Do() is nil

[benjivesterby]

@dustin-decker can you please rebase on current master branch so I can merge this?

[benjivesterby]

@dustin-decker Looks like you'll have to handle the conflicts here. I'm going to push a release without this change for now.

[dustin-decker]

Github says there are no conflicts with the base branch after you merged master into it.

[andygrunwald]

This is looking good! Thanks @dustin-decker

[benjivesterby]

This is looking good! Thanks @dustin-decker

The tests were broken so I just pushed a change to fix them. The merge on github wasn't complete like I thought.